1. Field of the Invention
The present invention relates to a lubricated bushing, and more particularly to a lubricated bushing that prevents a shaft mounted in the lubricated bushing from seizing up.
2. Description of the Prior Art
With reference to FIG. 6, a conventional lubricated bushing (30) is mounted in a mounting cavity in a bushing housing of a device such as a fan, rotatably holds a shaft and has a body (35) and a mounting sleeve (31).
The body (35) is cylindrical and has an axial hole (32), an outer end, an inner end and an outer wall. The axial hole (32) is formed coaxially through the body (35) and rotatably holds a shaft of a rotor of a fan and has an inner wall. The outer end of the body (35) has a concentric recess (38), multiple lubricant notches (36), an outer edge and an annular chamfer (37). The concentric recess (38) is formed in the outer end of the body (35) and communicates with the axial hole (32). The lubricant notches (36) are formed in the outer edge of the outer end of the body (35) at intervals and communicate with the concentric recess (38). When the shaft rotates, lubricant flows through the lubricant notches (36) and the concentric recess (38) into the axial hole (32) to lubricate the shaft. The lubricant reduces friction between the shaft and the inner wall of the axial hole (32), such that the shaft wears less and has a longer life. The annular chamfer (37) is formed on the outer edge of the outer end. The inner end of the body (35) is opposite to the first end.
The mounting sleeve (31) is longer than half the body (35), is formed around and protrudes from the outer wall of the body (35) of the lubricated bushing (30), is flush with the inner end of the body (35), abuts an inner wall of the mounting cavity in the bushing housing and allows lubricant to be stored in a gap between the body (35) and the mounting recess at the outer end of the body (35). The mounting sleeve (31) has two ends, an outer wall, two chamfers (33) and multiple lubricant grooves (34). The chamfers (33) are formed respectively on the ends of the mounting sleeve (31). The lubricant grooves (34) are formed longitudinally in the outer wall of the mounting sleeve (31), align respectively with the lubricant notches (36) and communicate with the end chamfers (33) on the ends of the mounting sleeve (31) to allow lubricant to flow to allow lubricant to circulate through the axial hole (32), concentric recess (38), lubricant notches (36) and lubricant grooves (34).
The conventional lubricated bushing (30) has a number of shortcomings. The shortcomings result in excessive operation noise, bearing seizing and limited lubrication capacity.
Squeezing the lubricated bushing (30) into a mounting cavity in a bushing housing compresses the mounting sleeve (31) somewhat, which easily deforms the axial hole (32) through the body (35) and causes the inner surface of the axial hole (32) to bind against the shaft mounted in the axial hole (32). This binding between the inner surface of the axial hole (32) and the shaft results in a loud noise when the shaft rotates and may cause the shaft seize up unexpectedly in the deformed axial hole (32).
Still further, because the lubricant grooves (34) respectively align with the lubricant notches (36), lubricant easily leaks out of the lubricated bushing (30) along the aligned lubricant notches (36) and lubricant grooves (34).
Additionally, the gap formed by the mounting sleeve (31) is limited to the outer end of the body (35), so only a limited amount of lubricant can be stored in the gap.
To overcome the shortcomings, the present invention provides a lubricated bushing to obviate or mitigate the aforementioned problems.